1. Field of the Invention
The present invention relates to a multifan-equipped apparatus and a method of controlling operation of a fan-unit assembly of the apparatus. More particularly the invention concerns an improvement of the apparatus and method which are suitable for cooling a plurality of electronic devices by a plurality of fan units mounted in a plurality of layers one over another in a chassis of the apparatus.
2. Description of the Related Art
Nowadays electronics manufacturers have made attempts to develop less-powered electronic devices, which work at a low voltage, as demands for saving energy in electronics to assist environmental protection are on the rise. But, it is now harder time to cope with the heat problem of modern electronics (each hereinafter also called the apparatus) because, in the individual apparatus, a multiplicity of electronic devices are mounted in a chassis with high-density, thanks to recent advance of mounting technology. To this end, it is now a common practice to use a cooling fan (hereinafter also called the fan) as an easy and less-expensive measure. Accordingly demand for fan-equipped electronics will increase.
However, it is particularly essential to minimize consumption of power due to installation of the fan as many of electronics manufacturers are reluctant to increase the price of the apparatus only for use of the fan. In the meantime, it is important to secure an adequate degree of cooling performance of the fan.
For efficient operation of the fan, it is preferable to control the fan in rpm (revolutions per minute) in accordance with a current apparatus-environment temperature and a current operating condition of the apparatus. Many of electronic manufacturers incorporate a temperature sensor with the fan (the resulting fan is called the fan unit) so that the fan is autonomically adjusted in rpm, depending on a current temperature detected by the temperature sensor.
It is a common knowledge that the cooling performance (rpm) of every cooling fan unit will become worse as the fan ages. Consequently, for a multifan-equipped apparatus in which a plurality of fan units are mounted within the chassis, some of electronics manufacturers made, upon occurrence of an abnormality in cooling performance (undue lowering of cooling performance) with a certain fan unit, a back-up control on at least one fan unit about the abnormal fan unit, which are normally operating under autonomic control, to increase the current rpm in an attempt to keep necessary performance of the whole cooling system.
Thus according to the last-mentioned conventional technology, it was intended to realize a balance between economical operation of the fan-unit assembly and a cooling redundancy to cope with possible lowering of cooping performance, by adopting the autonomic/back-up control system. This prior art is exemplified by Japanese Patent Laid-Open Publication No. 2000-346512.
FIG. 13 of the accompanying drawings shows a conventional multifan-equipped apparatus in which a plurality of electronic units (electronics) to be cooled are mounted in a chassis 40, for example, in the form of a multiplayer rack. In FIG. 13, three electronic units 10, 20, 30 are supported one on each of three layers in the chassis 40. And three sets of fan units, each set including four fan units 100-1 through 100-4, 200-1 through 200-4, 300-1 through 300-4, are mounted one set under each of the electronic units 10, 20, 30.
In this multi-layer fashion of mounting, because the electronic unit 10 (20) is sandwiched between two set of fan units, cooling air for the electronic unit 20 (30) disposed leeward of the electronic unit 10 (20) would rise somehow due to the heat radiated by the last-named windward electronic unit 10 (20).
For this reason, during operation of the fan units 100-i, 200-i, 300-i (i=a natural number selected from 1 through 4) under the above-mentioned autonomic control, the fan operation (rpm) would tend to be staggered between the individual fan units 100-i, 200-i, 300-i would fluctuate due to the difference in temperature between the upper and lower layers within the chassis 40 and the difference in amount of radiated heat of the leeward and windward electronic units 10, 20, 30 so that cooling air flows within the chassis 40 would be out of balance, thus impairing the cooling efficiency and increasing noises.
In other words, the temperature detected at and about the leeward fan unit 200-i (300-i) than that detected at and about the windward fan unit 100-i (200-i) so that the rpm value fluctuates between the upper and lower fan units as each fan unit is operating under autonomic control in accordance with the respective temperature detected, which would result in an inefficient cooling operation.
To avoid this staggering of rpm between the lower set of fan units 100-i (200-i) and the upper set of fan units 200-i (300-i), as shown in FIG. 14, all the fan units are individually monitored by a common cooling monitor 50. And the cooling monitor 50 serves also to adjust the rpm of an individual upper fan unit 200-i (300-i) to an individual lower fan unit 100-i (200-i), which is disposed windward of the last-named upper fan unit, so as to keep cooling air flows within the chassis 40 in balance (back-up control).
In this monitoring, the cooling monitor 50 non-interruptedly monitors the current operation statuses (occurrence of an error, mounting/dismounting, current operation mode (autonomic control or back-up control), etc.) of the fan units individually; the individual fan unit 100-i, 200-i, 300-i normally notifies the cooling monitor 50 of the current operation status of itself by a warning (ALM) signal, a dismounting (RMV) signal, a mode (MODE) signal, etc. Now assuming that an abnormality has occurred with a certain fan unit 100-i, 200-i, 300-i or a certain fan unit 100-i, 200-i, 300-i have been dismounted, the cooling monitor 50 makes a back-up control on a nearby fan unit 100-j, 200-j, 300-j (j=a natural number selected from 1 through 4, jxe2x89xa0i) by, for example, increasing the rpm of the last-named nearby fan unit to thereby keep the cooling performance of the whole fan-unit assembly.
In FIG. 14, arrow-headed lines are depicted with respect to the fan units 100-2, 200-2 (200-2, 200-3); the arrow-headed lines each indicates the direction in which a warning message is given from an individual fan unit 100-2 or 200-2 (200-2 or 200-3) to the cooling monitor 50 or the direction in which a back-up-control signal is given from the cooling monitor 50 to a nearby fan unit 200-1 or 100-2 (200-3 or 200-2). Also the solid arrow-headed line indicates that the warning message is given non-interruptedly, and the dotted arrow-headed line indicates that the back-up-control signal is given only upon occurrence of an error. (Similar lines with respect to the other fan units 100-1 (200-1), 200-1 (300-1), 100-3 (200-3), 200-3 (300-3), 100-4 (200-4), 200-4 (300-4) are omitted here for clarity of illustration.
For economical operation of the fan-unit assembly, the operation of the fan-unit assembly should be controlled preferably in accordance with the current apparatus-environment temperature as demand arises, and ideally linearly with the rise of the temperature. Practically, however, particularly under a sophisticated control environment in which cooling-air flows within the chassis 40 have to be kept in balance (back-up control), the conventional apparatus have no choice to adopt a non-linear and hence stepwise control, in which the rpm of the individual fan unit has to be changed stepwise to a selected one of a plurality of fixed values.
In this stepwise control, as shown in FIG. 15(B), a threshold value for the rpm of the individual fan should be incorporated with a hysteresis 70 to suppress possible flattering of the rpm due to the variations of in-apparatus temperature when the control mode is switched over. At that time, the hysteresis 70 has to be set for the rpm in accordance with around-fan-unit temperature; in such hysteresis 70, however, a sharp-rise-and-fall (in in-apparatus temperature) phenomenon as indicated by reference number 60, would inevitably occur due to the stepwise control, particularly when the rpm of the fan is changed from a low speed to a high speed and vice versa, as shown in FIG. 15(A).
Specifically, now assuming that the in-apparatus temperature rises with the increase of around-fan-unit temperature as the individual fan 100-i, 200-i, 300-i is driven at the low-speed (NL), the driven speed of the fan 100-i, 200-i, 300-i will be changed to the high speed (NH) when the current rpm reaches a predetermined threshold in-apparatus temperature, so that the in-apparatus temperature would rise and fall sharply as indicated by reference numeral 60 in FIG. 15(A). Because this phenomenon gives a temperature shock on the electronic units (or equipment) 10, 20, 30 to be cooled, the xe2x80x9cstepwise controlxe2x80x9d is not the most practical control for the fan units 100-i, 200-i, 300-i. 
On the other hand, in the linear-type control in which the rpm of the individual fan unit is controlled to vary linearly, it realizes a very efficient cooling operation. However, partly since the fan units 100-i, 200-i, 300-i as individually self-controlled encounter a fluttering phenomenon for their different positions of amounting, and partly since such fluttering makes cooling-air flows within the chassis out of balance, it was very difficult to realize a harmonized combination of the conventional autonomic control and the conventional back-up control.
Moreover, in an alternative multi-layer arrangement in which an increased number of fan units are mounted in an effort to improve the cooling performance, the load of control to be executed by the cooling monitor 50 would increase basically in proportion to the total number of the fan units so that it would be very hard to fulfill such duty control, depending on the form of mounting of the whole fan-unit assembly.
With the foregoing problems in view, it is a first object of the present invention to provide a multifan-equipped apparatus in which a fan-unit assembly can be efficiently controlled in agreement with both the current status of operation of the apparatus and the environment of the apparatus to reduce the total consumption of electronic power to a minimum, thus guaranteeing a less-expensive cooling operation without risk of damaging objects to be cooled.
A second object of the invention is to provide a method for controlling the cooling operation of the fan-unit assembly of the multifan-equipped apparatus less expensively with a minimum risk of damaging objects to be cooled.
According to one generic feature of the invention, the first object is accomplished by a multifan-equipped apparatus in which a plurality of objects mounted at different local interior regions are controllably cooled by blowing air, comprising: a fan-unit assembly, composed of a plurality of fan units that are divided into a plurality of groups disposed at the respective local interior regions, for blowing air over the objects to cool, the plural fan units in the same group being arranged in a queue along the corresponding local interior region or across the different interior regions; one of the plural fan units of each group being a master fan unit that is autonomically adjustable in revolutions per minute (rpm) in accordance with a current apparatus-environment temperature at the corresponding local interior region and serves to make a tuning control on the rpm of at least one of the remaining fan units in the same group so as to adjust the last-named rpm to a first estimated value corresponding to the autonomic-adjusted rpm of the master fan unit; and means for monitoring every fan unit of each group in state of operation and, if an error occurs in the state of operation of a fan unit of a group, setting the current rpm of the master fan unit of at least one necessary group to a second estimated value for a back-up control minimizing a possible loss of cooling performance of the fan-unit assembly due to the occurrence of the error.
As a specific feature, the master fan unit of each group may include:
(1) a temperature sensor for detecting the temperature;
(2) an autonomic controller for autonomically controlling the rpm of the last-named fan unit based on a predetermined rpm-control reference signal; and
(3) a first control-signal selector for selectively outputting a first control signal responsive to the temperature detected by the temperature sensor as the rpm-control reference signal to the autonomic controller and also as a tuning-control signal to the at least one remaining fan unit for the tuning control, and a second control signal, which is received from the monitoring means for the back-up control as the rpm-control reference signal to the autonomic controller and also as a tuning-control signal to the at least one remaining fan unit.
As another specific feature, every fan unit except the master fan unit in each group may include:
(1) a temperature sensor for detecting the temperature;
(2) an autonomic controller for autonomically controlling the rpm of the last-named fan unit based on a predetermined rpm-control reference signal; and
(3) a second control-signal selector for selectively outputting a first control signal responsive to the temperature detected by the temperature sensor as the rpm-control reference signal to the autonomic controller and also as a tuning-control signal to the at least one remaining fan unit for the tuning control, and a second control signal, which is received from the master fan unit or the monitoring means for the back-up control as the rpm-control reference signal to the autonomic controller and also as a tuning-control signal to the at least one remaining fan unit.
According to another generic feature of the invention, the first object is accomplished by a multifan-equipped apparatus in which a plurality of objects mounted at different local interior regions are controllably cooled by blowing air, comprising: a fan-unit assembly, composed of a plurality of fan units that are divided into a plurality of groups disposed across the different local interior regions, for blowing air over the object elements to cool, the plural fan units in the same group being arranged in a queue along a common air flow; one of the plural fan units of each group being a master fan unit that is autonomically adjustable in revolutions per minute (rpm) in accordance with an apparatus-environment temperature in the corresponding local interior region and serves to make a tuning control on the rpm of at least one of the remaining fan units in each said group so as to adjust the last-named rpm to a first estimated value corresponding to the autonomic-adjusted rpm of said master fan unit; and means for monitoring every fan unit of each group in state of operation and, if an error occurs in the state of operation of a fan unit of a group, setting the current rpm of said master fan unit of at least one necessary group to a second estimated value for a back-up control minimizing a possible loss of cooling performance of said fan-unit assembly due to the occurrence of the error.
According to still another generic feature of the invention, the first object is accomplished by a multifan-equipped apparatus in which a plurality of objects mounted at different local interior regions are controllably cooled by blowing air, comprising: a fan-unit assembly, composed of a plurality of fan units that are divided into a plurality of groups disposed along the respective local interior regions or across the different local interior regions, for blowing air over the objects to cool, the plural fan units in the same units being arrange in a queue and common indirection of blowing air; and means for monitoring every fan unit of each group in state of operation and, if an error occurs in the state of operation of a fan unit of a group, varying revolutions per minute (rpm) of the fan units of at least one necessary group in accordance with a current apparatus-environment temperature in the corresponding local interior region using common control information to an estimated value for necessary coordinated control minimizing a possible loss of cooling performance of the fan-unit assembly due to the occurrence of the error, thereby controlling the rpm of the fan units of the fan-unit assembly in terms of groups using the common control information for the same group.
According to a further generic feature of the invention, the second object is accomplished by a method of controlling operation of a fan-unit assembly of a multifan-equipped apparatus in which a plurality of objects mounted at different local interior regions are cooled by blowing air, comprising the steps of:
(a) dividing a plurality of fan units of the fan-unit assembly into a plurality of groups that are disposed along the respective local interior regions or across the different local interior regions for blowing air over the objects, the plural fan units of each group being arranged in a queue, one of the plural fan units of each group being a master fan unit;
at the master fan unit
(b) making an autonomic control on itself in revolutions per minute (rpm) in accordance with a current apparatus-environment temperature at the corresponding local interior region, and then making a tuning control on the rpm of at least one of the remaining fan units of the same group so as to adjust the last-named rpm to a first estimated value corresponding to the autonomic-adjusted rpm of the master fan unit;
(c) monitoring every fan unit of each group in state of operation; and
if an error occurs in the state of operation of a fan unit of a group
(d) setting the current rpm of the master fan unit of at least one necessary group to a second estimated value for a back-up control minimizing a possible loss of cooling performance of the fan-unit assembly due to the occurrence of the error.
According to another generic feature of the invention, the second object accomplished by a method of controlling operation of a fan-unit assembly of a multifan-equipped apparatus in which a plurality of objects mounted at different local interior regions are cooled by blowing air, comprising the steps of:
(a) dividing a plurality of fan units of the fan-unit assembly into a plurality of groups that are disposed along the respective local interior regions or across the different local interior regions for blowing air over the objects, the plural fan units of the same group being arranged in a queue along a common path of air flow, one of the plural fan units of each group as a master fan unit;
at the master fan unit
(b) making an autonomic control on itself in revolutions per minute rpm in accordance with a current apparatus-environment temperature at the corresponding local interior region, and then making a tuning control on the rpm of every remaining fan unit in the same group so as to adjust the last-named rpm to a first estimated value corresponding to the autonomic-adjusted rpm of the master fan unit; and
(c) monitoring every fan unit of each group in state of operation; and
if an error occurs in the state of operation of a fan unit of a group
(d) setting the current rpm of the master fan unit of at least one necessary group to an estimated value for a back-up control minimizing a possible loss of cooling performance of the fan-unit assembly due to the occurrence of the error.
According to an additional generic feature of the invention, the second object is accomplished by a method of controlling operation of a fan-unit assembly of a multifan-equipped apparatus in which a plurality of objects mounted at different local interior regions are cooled by blowing air, comprising the steps of:
(a) dividing a plurality of fan units of the fan-unit assembly into a plurality of groups that are disposed along the respective local interior regions or across the different local interior regions, for blowing air over the object element to cool, the plural fan units of the same group being common in direction of blowing air;
(b) monitoring every fan unit of each group in state of operation; and
if an error occurs in the state of operation of a fan unit of a group
(c) varying revolutions per minute (rpm) of the fan units of at least one necessary group in accordance with a current apparatus-environment temperature in the corresponding local interior region using common control information to an estimated value for necessary coordinated control minimizing a possible loss of cooling performance of the fan-unit assembly due to the occurrence of the error, thereby controlling the operations of the fan units of the fan-unit assembly in terms of groups using the common control information for the same group.
Following are advantageous results with the present invention:
(1) Partly because the master fan unit makes a tuning control on the rpm of at least one slave fan unit of the same group in accordance with the autonomic-adjusted self-fan rpm, and partly because the rpm of the master fan unit of a necessary group is set by a back-up control as demand arises, the tuning control and back-up control can be carried out in terms of groups. It is therefore possible not only to improve the cooling efficiency to a great extent with keeping cooling-air flows normally in balance but also to cope with cooling control by the fan-unit assembly, whichever they are arranged in a two-dimensional fashion or a three-dimensional fashion, thus facilitating the duty control (reducing the load of control) of the monitor/controller unit. As a result, a multifan-equipped apparatus having adequate cooling performance can be realized with reduced power consumption.
(2) Because the monitor/controller unit monitors every fan unit by periodically polling whether an error occurs with any fan unit in status of operation and, if an error has steadily occurred with the same fan unit for a predetermined time, then judges that such fan unit is in trouble, it is possible to realize an error detection with improved accuracy.
(3) Partly because the individual fan unit has not only a function of outputting a signal responsive to the temperature detected by itself as a self-fan rpm-control reference signal and a tuning-control signal to another fan unit of the same group, but also a function of outputting, upon receipt of a tuning-control signal from outside (the monitor/controller unit or another fan unit, the received control signal as a substitution for a self-fan rpm-control reference signal and a tuning-control signal to such another fan unit, respectively, tuning control can be realized in terms of groups. Further, transmission of a tuning-control signal can be performed independently of the controlling of the fan rpm and hence can be attained correctly irrespective of a possible occurrence of an error with the self-fan rpm.
(4) Because the individual fan unit is autonomically controlled (in rpm) linearly, it is possible to prevent any occurrence of sharp-rise-and-fall temperature, which would have encountered with the stepwise control in the prior art, so that any bad influence on the objects to be cooled can be effectively suppressed, guaranteeing a damage-less cooling operation.
(5) By comparing the voltage corresponding to the self-fan rpm with the output voltage of an rpm-control signal and feedback-controlling the self-fan rpm in such a manner that the voltage difference is minimal, it is possible to control the individual fan unit stably at a predetermined rpm even under an disturbance environment, such as fluctuation of supply voltage or variation of load torque of the fan due to the temperature change.
(6) Partly because the output voltage of the self-rpm detector, which is one of the two voltages to be compared in the feedback control, is filtered by the first filter circuit, and the voltage of an rpm-control reference signal, which is the other voltage to be compared in the feedback control, is filtered by the second filter circuit, and partly because a time constant present for the second filter circuit is larger than that preset for the first filter circuit, a response of the second filter circuit would delay behind that of the first filter circuit so that an undue oscillation in the feedback control can be avoided even when the rpm-control reference voltage fluctuates suddenly, thus realizing a stabilized rpm control.
(7) Because the linear-type autonomic control is attained by an analog circuit that includes the reference voltage circuit responsive to the self-fan rpm and the comparator/amplifier unit, which amplifies the voltage difference linearly, it is possible to reduce the price of the apparatus.
(8) Further, because the error detector also is attained by a simple analog circuit that includes the voltage converter for converting information about the self-fan rpm into a voltage value and the error detector for comparing the output voltage of the voltage converter with a threshold voltage value and discriminates, from the result of comparison, whether or not an error has occurred, it is advantageous to reduce the cost of production.
(9) By mounting the individual fan units on a substrate having a card-edge interface, which is electrically connectable to an external tester if fitted in the external tester, so that each fan unit receives a testing signal from the external tester, it is possible to have electric access to the individual fan unit from the external tester without increasing the number of pins of a mating connecter of the tester even when the individual fan unit to be tested is mounted not solely, facilitating the testing with minimum cost. Inserting (fitting) the card-edge interface of the substrate into the mating connector 14 of the external tester suffices to test, it is possible to carry out the testing operation with improved efficiency.
(10) By inputting, for example, a pseud rpm signal as the above-described testing signal from the external tester to the fan unit via the card-edge interface, it is possible to make an operation test of the error detector with ease.
(11) Given that one or more Ids respectively unique to one or more items to be tested are assigned to the card-edge interface, it is possible to automatically recognize from the external tester what is the object item, improving the efficiency of automated testing operation.
Other subjects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.